A stenosed site or an occluded site formed in the lumen of blood vessels, urethra, or the like, may be treated using a balloon. The balloon is inserted into the lumen and dilates at the stenosed site or the occluded site.
After the treatment, the balloon is deflated and removed from the lumen. In order to remove the balloon while suppressing damage caused to the inner wall of the lumen, it is desirable to deflate the balloon as much as possible.
For example, JP-A-2014-57793 suggests a method of deflating the balloon by folding it. According to the document, in the balloon, a plurality of “blade portions” are formed to protrude outwardly in a radial direction, and are separated from each other in a circumferential direction. The balloon is folded so that the portions between the blade portions deflate toward the inside in the radial direction.
However, because the size of the “blade portions” is approximately the same as or larger than the radius of the dilated balloon, the blade portions easily interfere with the lumen and hinder the removal of the balloon.
When the internal pressure of the balloon is reduced without folding the balloon, generally, the balloon is crushed and flattened. The width of the flattened cross-sectional shape in a major axis direction becomes greater than the outer diameter of the circular cross-section of the balloon before deflation.
In a case of a balloon used for pressing and bonding a therapeutic sheet onto the stenosed site of the urethra, the outer diameter of the balloon is designed to be greater than the inner diameter of the urethra because the therapeutic sheet needs to be uniformly bonded and pressed onto the stenosed site. Accordingly, if such a balloon is folded as it is in the related art, or if the internal pressure is simply reduced, the maximum width of the deflated balloon may be greater than the inner diameter of the urethra. In this case, the balloon and the inner wall of the urethra interfere with each other, and this makes it difficult to remove the balloon.